The critical event in the induction of cancer is widely believed to be the chemical binding of the ultimate carcinogen to the nucleic acid base residues. Degradation of nucleic acids exposed to these substances both in vitro and in vivo has revealed a wide variety of adducts of different types even for apparently related systems. However there currently exists no coherent theory of chemical reactivity capable of explaining this diverse behavior. The purpose of the proposed research is therefore to develop a methodology based on the application of semiempirical molecular orbital theory at the MNDO level and to seek ways to maximize the economy of such a procedure. The successful development of such a picture would provide unique insights into the reactions responsible for chemical carcinogenesis. To the extent that the genetic consequences of the various reactions become understood, prediction of mutagenicity from chemical structure would become an eventual consequence of this research.